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UCC28950: SLUA646: Frequency Dithering With the UCC28950 and TLV3201

Isaac Kreft
Prodigy 50 points
Part Number: UCC28950
Other Parts Discussed in Thread: UCC28951

Tool/software:

I'm trying to understand how to do frequency dithering according to the Application Report SLUA646. There seems to be an inconsistency with the orientation of the RT resistor (called R6 in the report). The Datashseet for UCC28950/UCC28951 calls for this resistor to be connected between VREF and the RT pin. In the report's Figure 1, this resistor is connected from the RT pin to Ground. In the report Figures 3 and Appendix 1, the resistor RT (R6) is connected from the RT pin to VREF. The report even says "With the controller set as a master, this resistor is tied from the Rt pin to the Vref pin which supplies a 5V source." Is Figure 1 wrong?

  • 0
    TI__Guru* 86286 points

    Hello,

     

    The inquiries will be evaluated in the order they have been received.

     

    Regards,

  • 0 in reply to Mike O'
    TI__Intellectual 1150 points

    Hi Isaac,

    As mentioned in the datasheet, connecting RT and Vref pin through a resistor makes the controller in master mode and connecting RT pin and ground through a resistor makes the controller in follower mode. The figure 1 in application note is an example for frequency dithering circuit when the controller is in follower mode and figure 3 & appendix 1 are example for frequency dithering circuit when the controller is in master mode. 

    I hope this clears the confusion.

    Regards,
    Deepak K